a precious stone such as the transparent emerald (see Molina; Engl. transl. by SW)
Orthographic Variants:
ompa ontlaneci chalchiuitl
Alonso de Molina:
ompa ontlaneci chalchiuitl. piedra preciosa casi como esmeralda trasparente. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 76v. col. 2. Thanks to Joe Campbell for providing the transcription.